Regulatory Matters (Details)											1 Months Ended		2 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	Jun. 01, 2016 USD ($)	Feb. 01, 2016 $ / kWh	Jan. 15, 2016 USD ($)	Jan. 01, 2016 USD ($)	Jun. 01, 2015 USD ($)	Mar. 02, 2015 USD ($)	Nov. 04, 2014	Mar. 01, 2014 USD ($)	Jan. 01, 2014 USD ($) $ / kWh	Jan. 06, 2012 USD ($) $ / kWh	Sep. 30, 2016 USD ($) phase	Dec. 31, 2014 USD ($) penetration_feeder storage_system MW	Apr. 30, 2014 workshop	Jan. 31, 2016 $ / kWh	Sep. 30, 2016 USD ($) $ / kWh	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) $ / kWh	Jul. 12, 2016 USD ($)	Jul. 01, 2016 USD ($)	Apr. 01, 2016 USD ($)	Jan. 12, 2016 USD ($)	Nov. 25, 2015 USD ($)	Mar. 20, 2015 project
Change in regulatory asset
Deferred fuel and purchased power costs — current period															$ 46,185,000	$ 137,000
Amounts charged to customers															(28,366,000)	(19,284,000)
APS
Change in regulatory asset
Deferred fuel and purchased power costs — current period															46,185,000	137,000
Amounts charged to customers															$ (28,366,000)	(19,284,000)
RES 2014 | APS | Alternative to AZ Sun Program, Phase 1
Settlement Agreement
Request to build additional utility scale solar, capacity | MW												8
RES 2014 | APS | Alternative to AZ Sun Program Phase 2
Settlement Agreement
Request to build additional utility scale solar, capacity | MW												2
Number of energy storage systems | storage_system												2
Number of high solar penetration feeders | penetration_feeder												2
Lost Fixed Cost Recovery Mechanisms | APS
Change in regulatory asset
Fixed costs recoverable per residential power lost (in dollars per kWh) | $ / kWh															0.031
Fixed costs recoverable per non-residential power lost (in dollars per kWh) | $ / kWh															0.023
Percentage of retail revenues											1.00%				1.00%
Amount of adjustment representing prorated sales losses approval			$ 46,400,000			$ 38,500,000		$ 25,300,000
Increase in amount of adjustment representing prorated sales losses			$ 7,900,000
ACC | Retail Rate Case Filing with Arizona Corporation Commission | APS
Settlement Agreement
Net change in base rates										$ 0
Non-fuel base rate increase										116,300,000
Fuel-related base rate decrease										$ 153,100,000
Current base fuel rate (in dollars per kWh) | $ / kWh										0.03757
Approved base fuel rate (in dollars per kWh) | $ / kWh										0.03207
Estimated amount of transfer of cost recovery for certain renewable energy projects from the RES surcharge to base rates										$ 36,800,000
Authorized return on common equity (as a percent)										10.00%
Percentage of debt in capital structure										46.10%
Percentage of common equity in capital structure										53.90%
Deferral of property taxes in 2012, if Arizona property tax rates increase (as a percent)										25.00%
Deferral of property taxes in 2013, if Arizona property tax rates increase (as a percent)										50.00%
Deferral of property taxes for 2014 and subsequent years, if Arizona property tax rates increase (as a percent)										75.00%
Deferral of property taxes in all years, if Arizona property tax rates decrease (as a percent)										100.00%
Elimination of the sharing provision of fuel and purchased power costs										9
Period to process the subsequent rate cases										12 months
ACC staff sufficiency findings, general period of time										30 days
Change in regulatory asset
Reduced system benefits charge, amount				$ 14,600,000
ACC | Retail Rate Case Filing with Arizona Corporation Commission | APS | Maximum
Settlement Agreement
Annual cost recovery due to modifications to the Environmental Improvement Surcharge										$ 5,000,000
ACC | RES | APS
Settlement Agreement
Plan term															5 years
ACC | RES 2016 | APS
Settlement Agreement
Amount of approved budget																					$ 148,000,000
ACC | RES 2017 | APS
Settlement Agreement
Amount of proposed budget																			$ 150,000,000
ACC | Modernization and Expansion of the Renewal Energy Standard [Member] | APS
Settlement Agreement
Proposed renewal energy standard, percent of retail sales											30.00%
Current renewal energy standard, percent of retail sales											15.00%
ACC | DSMAC 2015 | APS
Settlement Agreement
Amount of approved budget																				$ 68,900,000		$ 68,900,000
Additional budget approved																		$ 4,000,000
Number of resource savings projects | project																							3
ACC | DSMC 2016 | APS
Settlement Agreement
Amount of approved budget					$ 68,900,000
ACC | Electric energy efficiency standard | APS
Settlement Agreement
Number of workshops | workshop													3
Number of days to convene a workshop							120 days
ACC | Power Supply Adjustor (PSA) | APS
Change in regulatory asset
Beginning balance				$ (9,688,000)											$ (9,688,000)	6,925,000	$ 6,925,000
Deferred fuel and purchased power costs — current period															46,185,000	137,000
Amounts charged to customers															(28,365,000)	(19,284,000)
Ending balance											$ 8,132,000	$ 6,925,000			$ 8,132,000	$ (12,222,000)	$ (9,688,000)
PSA rate (in dollars per kWh) | $ / kWh		0.001678
PSA rate for prior year (in dollars per kWh) | $ / kWh																	0.000887
Forward component of increase in PSA (in dollars per kWh) | $ / kWh		0.001975
Historical component of increase in PSA (in dollars per kWh) | $ / kWh		(0.000297)
Transition component increase in PSA (in dollars per kWh) | $ / kWh														(0.004936)
ACC | Net Metering | APS
Change in regulatory asset
Charge on future customers who install rooftop solar panels (in dollars per kWh) | $ / kWh									0.70						0.70
Rate matter case, umber of filing phases | phase											2
Estimated monthly collection due to charge on future customers who install rooftop solar panels									$ 4.90
United States Federal Energy Regulatory Commission | Open Access Transmission Tariff [Member] | APS
Change in regulatory asset
Decrease in annual wholesale transmission rates					$ 17,600,000
Increase in annual wholesale transmission rates	$ 24,900,000